This invention relates generally to rotary heat exchangers. More particularly, the present invention relates to a device for the lifting of baskets having heat transfer elements into and out of such air preheaters.
Conventional rotary regenerative air preheaters are commonly employed to transfer heat from the flue gases exiting a furnace to the incoming combustion air. Rotary regenerative preheaters have a rotor rotatably mounted in a casing or housing. The rotor supports heat exchange element basket assemblies, each having stacked heat transfer plates for the absorption of heat from a hot flue gas stream extinguish the furnace.
Generally, a heat exchange element basket assembly supports the heat exchange elements in a frame work having end plates. The end plates include one or more lifting lugs which allow the heat exchange element basket assemblies to be lifted into or out of the compartments of the air preheater rotor by a crane or other lifting apparatus. Presently, the lifting lugs have to be removed after the basket assembly is installed, to prevent interference with adjacent basket or rotor structure. Due to erosion and corrosion, the basket assemblies will be typically replaced multiple times during the operational life of an air preheater. The lifting lugs must be re-welded to the baskets prior to replacement of the baskets and removed from the baskets after replacement, thereby increasing the cost and time required to replace the heat exchange element basket assemblies.
Briefly stated, the invention in a preferred form is a cover for a heat exchange element basket assembly which includes a metal sheet and at least one lifting lug. A vertical groove extends,inward from the outer surface of the metal sheet. Each lifting lug comprises a horizontal plate having an opening extending vertically there through, an outer edge, and a shape which is substantially complementary to the cross-sectional profile of the groove. The lifting lug is mounted within the groove, such that the outer edge of the lifting lug does not extend beyond the outer surface of the metal sheet.
Preferably, the groove has a V-shape and the plate has a trapezoid shape, with the side edges of the lifting lug being welded to the sides of the groove.
First and second lifting lugs may be mounted in upper and lower portions of the groove. Alternatively, a single lifting lug may be mounted within the groove at the vertical centerline.
The outer edge of the lifting lug may be recessed behind the outer surface of the metal sheet. Alternatively, the outer edge of the lifting lug may be flush with the outer surface of the metal sheet.
It is an object of the invention to provide a cover for a heat exchange element basket assembly which does not require modification in the field each time the assembly is installed or removed.
It is also an object of the invention to provide a cover for a heat exchange element basket assembly which has additional rigidity.
It is further an object of the invention to provide a cover for a heat exchange element basket assembly which has lifting lugs which are permanently installed in a controlled and reliable shop environment.